Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$143.42	3.231%	$148.0539	$148.05	$148.05	$148.10
Purchase #2	$52.89	12.364%	$59.4293	$59.43	$59.45	$59.40
Purchase #3	$150.25	12.649%	$169.2551	$169.26	$169.25	$169.30
Purchase #4	$146.91	4.813%	$153.9808	$153.98	$154.00	$154.00
Purchase #5	$85.82	5.446%	$90.4938	$90.49	$90.50	$90.50
Purchase #6	$61.93	10.703%	$68.5584	$68.56	$68.55	$68.60
Purchase #7	$186.79	8.810%	$203.2462	$203.25	$203.25	$203.20
7 purchase totals =	$828.01		$893.0175	$893.02	$893.05	$893.10